The present invention relates generally to the field of implantable stimulators and more particularly to cardiac pacemakers and implantable anti-arrhythmia devices.
It has been proposed to reduce the incidence of tachyarrhythmias in the ventricle by using multiple site pacing. For example, in U.S. Pat. No. 3,937,226, issued to Funke, multiple electrodes are provided for location around the ventricles. In response to a sensed depolarization following a refractory period, at any of the electrodes, all electrodes are paced. All electrodes are similarly paced in the absence of sensed depolarizations for a period of 1000 ms. U.S. Pat. No. 4,088,140 issued to Rockland et al discloses a similar device, in which a pacing pulse is delivered only to a single electrode in response to a failure to sense during a 1000 ms period, and delivery of pacing pulses to multiple electrodes is triggered in response to sensed depolarizations occurring between 150 and 500 ms following delivery of a previous sensed depolarization or pacing pulse. U.S. Pat. No. 4,354,497, issued to Kahn adds sensing electrodes adjacent the septum of the heart and delivers pacing pulses to multiple electrodes spaced around the ventricles in response to sensed depolarizations at the ventricular electrodes which are not preceded by depolarizations sensed at the septum electrodes. Multi-site pacing in the ventricles has also been proposed to improve hemodynamic function, as in U.S. Pat. No. 4,928,688, issued to Mower. The Funke, Kahn, Rockland and Mower patents are all hereby incorporated herein by reference in their entireties.
Multi-site atrial pacing has also been proposed as a mechanism for reducing the incidence of atrial tachyarrhythmias. For example, multi-site pacing for arrhythmia prevention is discussed in U.S. Pat. No. 5,584,867, issued to Limousin et at, U.S. Pat. No. 5,683,429 issued to Mehra and U.S. Pat. No. 5,403,356, issued to Hill et al. and in the article "Prevention of Atrial Tachyarrhythmias Related to Advanced Inter-atrial Block by Permanent Atrial Resynchronization", by Mabo, et al, published in Pace, Vol. 14, April 1991, Part II, p 648. The Limousin, Mehra and Hill et al. patents are hereby incorporated herein by reference in their entireties.
Pacing methodologies employing only a single pacing site have also been proposed for prevention of tachyarrhythmias. For example, U.S. Pat. No. 4,941,471 issued to Mehra discloses a single site rate stabilization pacing method for use in the ventricles. An improvement to this pacing methodology is disclosed in U.S. Pat. No. 5,545,185 issued to Denker et al, and further improvements are disclosed in U.S. Pat. No. 5,814,085 issued to Hill, and U.S. patent application Ser. No. 08/764,568, filed on Dec. 16, 1996 by Peterson et al. An additional atrial overdrive arrhythmia prevention pacing mode which is disclosed in U.S. Pat. No. 5,713,929, issued to Hess et al. The Mehra, Hill, Hess et al. and Denker patents, as well as the Peterson et al. application are all hereby incorporated herein by reference in their entireties.